Tackifiers are materials that have a characteristic of immediate tackiness or stickiness. Tackifiers can be used in a wide variety of applications, and often form a major component of adhesive compositions. Examples of tackifiers include rosins, terpenes and modified terpenes, petroleum-derived resins, terpene-phenol resins, and silicone resins. Tackifiers can be expensive, and are frequently the most costly component of adhesive formulations. Tackifiers are frequently derived from non-biorenewable materials.